Hybrid mixtures for gas hydrate inhibition applications

ABSTRACT

A method of inhibiting gas hydrates comprises contacting gas hydrates with a hybrid mixture including a copolymer of at least one ethylenically unsaturated monomer and a naturally derived hydroxyl containing chain transfer agent.

FIELD OF THE INVENTION

The present invention relates to a method of inhibiting gas hydrates comprising contacting gas hydrates with a hybrid mixture comprising a derivative of at least one ethylenically unsaturated monomer and a naturally derived hydroxyl containing chain transfer agent.

BACKGROUND

Gas hydrates, also called clathrate hydrates, are crystalline water-based solids physically resembling ice, in which small non polar molecules (typically gases) are trapped inside “cages” of hydrogen bonded water molecules. Most low molecular weight gases (including O₂, H₂, N₂, CO₂, CH₄, H₂S, Ar, Kr, and Xe), as well as some higher hydrocarbons, form hydrates at suitable temperatures and pressures. Undesirably, gas hydrates may occur when water is present in mineral oil mixtures or in natural gas mixtures in which gas hydrate crystals may agglomerate and plug, for example, pipelines.

To inhibit gas hydrate formation, certain polymers or copolymers have been used to inhibit gas hydrate formation. However, increasingly stringent regulations regarding toxicity and degradability of oilfield chemicals and polymers have made conventional gas hydrate inhibitors less desirable. The leading conventional gas hydrate inhibiting polymers are not readily biodegradable under the conditions specified by the regulatory bodies. Thus, there is a need to provide improved gas hydrate inhibitors to meet the industries' needs.

SUMMARY OF THE INVENTION

Accordingly, it has been found that hybrid mixtures according to the present invention can address the problems associated with conventional gas hydrate inhibitors, including improving biodegradability. Hybrid mixtures comprise a naturally occurring oligomer or polymer and a synthetically derived oligomer or polymer. In addition, new combinations of naturally derived hydroxyl containing chain transfer agents in gas hydrate inhibition applications have been discovered that were heretofore previously unknown.

In an aspect, the invention is directed to a method of inhibiting gas hydrates comprising contacting a gas hydrate with a hybrid mixture comprising a derivative of at least one ethylenically unsaturated monomer and a naturally derived hydroxyl containing chain transfer agent. In a first embodiment, the derivative of the at least one ethylenically unsaturated monomer is a polymer including the ethylenically unsaturated monomer. In a second embodiment, the derivative is a polymeric chain comprised of the ethylenically unsaturated monomer that is attached covalently to the naturally derived hydroxyl containing chain transfer agent. In a further embodiment, the derivative may include a combination of the first and second embodiments.

In another aspect, the invention is directed to a method of inhibiting gas hydrates comprising contacting a gas hydrate with a hybrid mixture formed by combining at least one ethylenically unsaturated monomer with a solution of a naturally derived hydroxyl containing chain transfer agent and an initiator at a temperature effective to activate the initiator.

BRIEF DESCRIPTION OF THE DRAWING

The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings is the following FIGURE:

The FIGURE is a chart illustrating rapid hydrate formation time and temperature data from the evaluation of the hybrid mixture of Synthesis Example 24.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the invention is directed to a method of inhibiting gas hydrates. The method includes contacting the gas hydrates with a hybrid mixture. The hybrid mixtures of the instant invention are formed by combining at least one ethylenically unsaturated monomer with a solution containing a naturally derived hydroxyl containing chain transfer agent and an initiator at a temperature effective to activate the initiator.

In an aspect, the invention relates to a method of inhibiting gas hydrates wherein the method comprises contacting a gas hydrate with a hybrid mixture comprising a derivative of at least one ethylenically unsaturated monomer and a naturally derived hydroxyl containing chain transfer agent. In an embodiment, the hybrid mixture that is used to inhibit gas hydrates is an intimate mixture of at least one naturally derived hydroxyl containing chain transfer agent and a polymer comprised of at least one ethylenically unsaturated monomer. This intimate mixture can be prepared by polymerization of the at least one ethylenically unsaturated monomer, by means known to those skilled in art, in the presence of the at least one naturally derived hydroxyl containing chain transfer agent.

The intimate mixture can also be prepared by coprocessing the at least one naturally derived hydroxyl containing chain transfer agent with the polymer comprised of at least one ethylenically unsaturated monomer under conditions of high temperature or pressure or both. An example of coprocessing under conditions of high pressure and high temperature is to co jet cook the at least one naturally derived hydroxyl containing chain transfer agent with the polymer comprised of at least one ethylenically unsaturated monomer. Another example of coprocessing is heating the at least one naturally derived hydroxyl containing chain transfer agent with the polymer comprised of at least one ethylenically unsaturated monomer in aqueous solution under atmospheric pressure. In an embodiment, the derivative of the at least one ethylenically unsaturated monomer is a polymer including the ethylenically unsaturated monomer.

In another embodiment, the hybrid mixture is a hybrid copolymer composition prepared by reacting at least one ethylenically unsaturated monomer with a solution of a naturally derived hydroxyl containing chain transfer agent and an initiator. One conventional method of making hybrid mixtures utilizes water soluble monomers in the presence of an aqueous solution of a naturally derived, hydroxyl containing material as a chain transfer agent. Such a method is disclosed in U.S. Patent application publication number US 2007-0021577 A1, which is wholly incorporated herein by reference. In an embodiment, the derivative is a polymeric chain comprised of the ethylenically unsaturated monomer that is attached covalently to the naturally derived hydroxyl containing chain transfer agent.

In this embodiment, the hybrid copolymer composition can be prepared with a naturally derived hydroxyl containing chain transfer agent and still maintain the functionality of the synthetic polymers portion. Without wishing to be bound by theory, in this embodiment, it is believed that the reaction proceeds according to the following mechanism:

In the first step the initiator I forms free radicals which reacts with the monomer and initiates the synthetic polymer chain. This then propagates by reacting with several monomer moieties. Termination is then by chain transfer which abstracts a proton from the chain transfer agent. This terminates the hybrid synthetic polymer (a) and produces a free radical on the chain transfer agent. The chain transfer agent then reacts with several monomer moieties to form a species in which the naturally derived hydroxyl containing chain transfer agent is connected to the synthetic polymer chain. This species can then terminate by chain transfer mechanism or reaction with an initiator fragment or by some other termination such as combination or disproportionation reaction to produce the hybrid copolymer (b). If the termination is by chain transfer, then R₁ is H (abstracted from the chain transfer moiety) and the chain transfer agent can then initiate another chain.

Accordingly, as shown in the above reaction, a “hybrid copolymer composition” is a mixture of (a) a hybrid synthetic copolymer and (b) a hybrid copolymer. The hybrid copolymer composition thus contains the two moieties, (a) and (b), with a minimum amount of the hybrid synthetic copolymer (a) since this component generates the chain transfer which leads to the formation of the hybrid copolymer (b). One skilled in the art will recognize that the hybrid copolymer composition may contain a certain amount of the unreacted chain transfer agent.

The term “hybrid copolymer”, as defined herein, refers to a copolymer of synthetic monomers with an end group containing the naturally derived hydroxyl containing chain transfer agent which is a result of the hybrid synthetic copolymer chain transfer. The term “naturally derived hydroxyl containing chain transfer aged' as used herein, means a hydroxyl containing moiety obtained from plant sources directly or by enzymatic or fermentation processes. In an embodiment of the invention, the hybrid copolymer has the following structure:

where C is a moiety derived from the naturally derived hydroxyl containing chain transfer agent, M_(hc) is the synthetic portion of the hybrid copolymer derived from one or more ethylenically unsaturated monomers and R₁═H from chain transfer or I from reaction with the initiator radical or the naturally derived hydroxyl containing chain transfer agent or another moiety formed from a termination reaction.

In an embodiment, the attachment point between C and M_(hc) is through an aldehyde group in C which results in the link between C and M_(hc) being a carbonyl moiety. In another embodiment, when the naturally derived hydroxyl containing chain transfer agent is a saccharide/polysaccharide with an aldehyde group as the reducing end group, then the hybrid copolymer can be represented by the structure:

Where S is a saccharide repeat unit from the saccharide/polysaccharide chain transfer agent and s is an integer from 0 to 1000 and p is an integer that is 3, 4 or 5. In another embodiment, when the naturally derived hydroxyl containing chain transfer agent is an oxidized starch which contains aldehyde groups, the hybrid copolymer can be represented by the structure:

Also as used herein, the term “hybrid synthetic copolymer” is a synthetic polymer derived from synthetic monomers with a hybrid initiator fragment as one end group. The other end group is a proton resulting from chain transfer to the naturally derived hydroxyl containing chain transfer agent. As used herein, the term “synthetic monomer” means any ethylenically unsaturated monomer which can undergo free radical polymerization.

In an embodiment of the invention, an exemplary hybrid synthetic copolymer has the following structure:

Where I is the initiator fragment, H is the proton abstracted from the natural chain transfer agent and M_(hsc) is the synthetic portion of the hybrid synthetic copolymer derived from one or more ethylenically unsaturated monomers. One skilled in the art will recognize that if one or more ethylenically unsaturated monomers are used, the average composition of M_(hsc) and M_(hc) will be the same.

One skilled in the art will recognize that the hybrid initiator fragment incorporated into the hybrid synthetic copolymer will depend on the hybrid initiator used. For example, sodium persulfate, potassium persulfate and ammonium persulfate will incorporate sulfate initiator fragments, whereas an azo initiator, such as 2,2′-Azobis(2-methylpropionamidine)dihydrochloride, will incorporate a 2-methyl propane propionamidine hydrochloride fragment.

One skilled in the art will recognize, that the minimum amount of the hybrid synthetic copolymer will depend on the relative amounts of synthetic monomer, initiator and naturally derived hydroxyl containing chain transfer agent.

In an embodiment, a secondary chain transfer agent may also be included. The secondary chain transfer agent may be less than 20 weight percent of the hybrid polymer. In another embodiment, solution of the naturally derived hydroxyl containing chain transfer agent may be substantially free of secondary transfer agents. The process may further comprise catalyzing the polymerizing step with an initiator that is substantially free of a metal ion initiating system at a temperature sufficient to activate said initiator.

Molecular weight of the hybrid synthetic polymer is determined by the relative amounts of synthetic monomer, initiator and naturally derived hydroxyl containing chain transfer agent.

Optionally, in an embodiment of the present invention, the weight average molecular weight of the hybrid copolymer composition may be less than about 500,000, preferably less than 300,000 and most preferably less than 100,000. In a further embodiment, the hybrid copolymer composition may be water soluble. For purposes of the present application, water soluble is defined as having a solubility of greater than about 0.1 grams per 100 grams of water at 25° C. and preferably 1 gram per 100 grams of water at 25° C.

In another embodiment, the hybrid synthetic copolymer will have a hybrid initiator fragment (I) and some of the hybrid copolymer chains will have a natural chain transfer agent at one end and a hybrid initiator fragment (where R₁ is I) at the other end of the synthetic polymer chain. As used herein, the term “hybrid initiator fragment” is any fragment of the hybrid initiator that gets incorporated into a synthetic polymer derived from a hybrid initiator. In an embodiment, I is preferably 0.01 to 20 mole % of M_(hc)+M_(hsc) and more preferably I is 0.1 to 15 mole % of M_(hc)+M_(hsc) and most preferably I is 1 to 10 mole % of M_(hc)+M_(hsc).

In an embodiment of the invention, the naturally derived hydroxyl containing chain transfer agents include, but are not limited, to small molecules such as glycerol, citric acid, lactic acid, tartaric acid, gluconic acid, ascorbic acid, and glucoheptonic acid. The naturally derived hydroxyl containing chain transfer agents may also include saccharides or derivatives thereof. Suitable saccharides include, for example, monosaccharides and disaccharides such as sugars, such as glucose, galactose, mannose, fructose, arabinose, xylose, maltose, lactose, trehalose, cellobiose, maltotriose, and sucrose, as well as larger molecules such as oligosaccharides and polysaccharides (e.g., corn syrup solids, maltodextrins, pyrodextrins and starches). In an embodiment of the invention, the naturally derived chain transfer agent is maltodextrin, pyrodextrin or a low molecular weight starch. It has been found that the chain transfer reaction does not work well when the chain transfer agent is not soluble in the system. For example, high molecular weight starches, such as those having molecular weights in the millions or those in granular form, are water dispersible and not water soluble. Accordingly, in embodiments of the invention, the average molecular weight of the chain transfer agent is preferably less than about 500,000 based on a starch standard. Starches having such exemplary molecular weights are water soluble. In another embodiment, the average molecular weight (Mw) of the chain transfer agent may be less than about 100,000. In yet another preferred embodiment, the weight average molecular weight of the chain transfer agent may be less than about 50,000. In yet another preferred embodiment, the weight average molecular weight of the chain transfer agent may be less than about 10,000. It has also been determined that for applications in which dispersancy and scale control is particularly desirable, a lower molecular weight, such as 10,000, of the chain transfer agent provides improved performance.

The molecular weight of the polysaccharide was determined by the procedure outlined below:

-   -   Eluent: 0.025M NaH₂PO₄, 0.025 M Na₂HPO₄ and 0.01M of Sodium         Azide in HPLC grade water. This solution was filtered through a         0.2 μm filter.     -   Columns: 1 x G6000PWx1 7.8 mm×30 cm,G4000PWx1 7.8×30 cm,         G3000PWx1         -   7.8 mm×30 cm, Guard column is TSKgel Guard PWx1 6.0 mm×4 cm             (all made by Tosoh Bioscience)         -   The column bank was controlled to 5° C. above ambient             temperature. Usually 30° C.     -   Flow Rate: 1.0 ml/min     -   Detector: Refractive Index, Waters® Model 2414 Temperature         controlled to 30° C.     -   Pump/Autosampler: Waters® e2695 Separation Module. Sample         compartment temperature controlled to 25° C.     -   Primary Standards: HETA (Hydroxyethylstarch). Available from         American Polymer Standards Corporation. (www.ampolymer.com) 5         standards. Prepare a 0.1% w/w in the mobile phase of each of the         following:

1. Mw 9,600 Mn 5,400 2. Mw 25,900 Mn 10,600 3. Mw 51,100 Mn 34,300 4. Mw 114,300 Mn 58,000 5. Mw 226,800 Mn 95,900

-   -   Sample Preparation: The samples were prepared by dissolving the         polymer in the mobile phase at a 0.1% concentration.     -   Injection Volume: 450 μl for the standard and sample.         -   The standards are injected and a first or second order             calibration curve is built.         -   The curve with the best fit and within the range of the             molecular weight of the unknown sample was then chosen.     -   Software: Empower® 2 by Waters Corporation         -   A calibration curve is first built with the samples of the             standards. The molecular weight of the unknown sample is             then determined by comparing its elution time with the             elution time of the standards.

The naturally derived hydroxyl containing chain transfer agents also may include cellulose and its derivatives, as well as inulin and its derivatives, such as carboxymethyl inulin. The cellulosic derivatives include plant heteropolysaccharides commonly known as hemicelluloses which are by products of the paper and pulp industry. Hemicelluloses include xylans, glucuronoxylans, arabinoxylans, arabinogalactans, glucomannans, and xyloglucans. Xylans are the most common heteropolysaccharide and are preferred. In an embodiment of the invention, cellulosic derivatives such as heteropolysaccharides such as xylans may be present in an amount of from about 0.1% to about 98% by weight, based on the total amount of the hybrid copolymer. In an embodiment of this invention the naturally derived chain transfer agents may be maltodextrins, pyrodextrins and chemically modified versions of maltodextrins and pyrodextrins. In another embodiment, the naturally derived chain transfer agent may be cellulose of inulin or chemically modified cellulose or inulin or a heteropolysaccharide such as xylan or a lignin derivative, such as lignosulfonate.

The naturally derived hydroxyl containing chain transfer agents also may include polysaccharides and polysaccharide gums. Examples of polysaccharides and polysaccharide gums include but are not limited guar gum, locust bean gum, gum arabic alginic acid, pectin, chitin, chitosan, xanthan gum, and tamarind kernel gum.

The naturally derived chain transfer agents can be used as obtained from their natural source or they can be chemically modified. Chemical modification includes hydrolysis by the action of acids, enzymes, oxidizers or heat, esterification or etherification. The modified naturally derived chain transfer agents, after undergoing chemical modification may be cationic, anionic, non-ionic or amphoteric or hydrophobically modified. In an embodiment of the invention, the hybrid copolymer may optionally be formed by polymerization catalyzed by, for example, a non-metal based radical initiator system.

In an embodiment of the present invention, the gas hydrate inhibitor comprises a hybrid mixture wherein the derivative of the at least one ethylenically unsaturated monomer includes at least one anionic ethylenically unsaturated monomer. As used herein, the term “anionic ethylenically unsaturated monomer” means an ethylenically unsaturated monomer which is capable of introducing a negative charge to the anionic hybrid mixture. These anionic ethylenically unsaturated monomers can include, but are not limited to, acrylic acid, methacrylic acid, ethacrylic acid, α-chloro-acrylic acid, α-cyano acrylic acid, β-methyl-acrylic acid (crotonic acid), α-phenyl acrylic acid, β-acryloxy propionic acid, sorbic acid, α-chloro sorbic acid, angelic acid, cinnamic acid, p-chloro cinnamic acid, β-styryl acrylic acid (1-carboxy-4-phenyl butadiene-1,3), itaconic acid, maleic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, fumaric acid, tricarboxy ethylene, muconic acid, 2-acryloxypropionic acid, 2-acrylamido-2-methyl propane sulfonic acid, vinyl sulfonic acid, sodium methallyl sulfonate, sulfonated styrene, allyloxybenzene sulfonic acid, vinyl phosphonic acid and maleic acid. Moieties such as maleic anhydride or acrylamide that can be derivatized (hydrolyzed) to moieties with a negative charge are also suitable. Combinations of anionic ethylenically unsaturated monomers can also be used. In an embodiment of the invention, the anionic ethylenically unsaturated monomer may preferably be acrylic acid, maleic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methyl propane sulfonic acid or mixtures thereof.

In an embodiment, the anionic hybrid mixture comprises an anionic hybrid copolymer composition, which may contain 1 to 99.5 weight percent of the naturally derived hydroxyl containing chain transfer agent based on the weight of the hybrid copolymer mixture. Based on the conventional understanding of one of ordinary skill in the art, one would expect that the performance of the inventive anionic hybrid copolymer mixtures would decrease as the weight percent of the chain transfer agent in the polymer increases. For example, polysaccharides have little to no performance as dispersants by themselves. Surprisingly, however, it has been found that when the chain transfer agent content of the polymer is greater than 50 weight percent or more of the hybrid mixture, performance is still maintained.

In another embodiment, the present invention relates to gas hydrate inhibitors comprising hybrid mixtures in which the at least one ethylenically unsaturated monomer includes at least one non-anionic ethylenically unsaturated monomer. A hybrid mixture that is non-anionic, as used herein, includes mixtures produced from at least one cationic ethylenically unsaturated monomer or at least one nonionic ethylenically unsaturated monomer or a combination of cationic and non-ionic ethylenically unsaturated monomers and a naturally derived hydroxyl containing chain transfer agent. In an embodiment, the “cationic ethylenically unsaturated monomer” is capable of introducing a positive charge to a non-anionic hybrid mixture. In an embodiment of the present invention, the cationic ethylenically unsaturated monomer has at least one amine functionality. Cationic derivatives of non-anionic hybrid copolymer compositions may be formed by forming amine salts of all or a portion of the amine functionality, by quaternizing all or a portion of the amine functionality to form quaternary ammonium salts, or by oxidizing all or a portion of the amine functionality to form N-oxide groups.

As used herein, the term “amine salt” means the nitrogen atom of the amine functionality is covalently bonded to from one to three organic groups and is associated with an anion.

As used herein, the term “quaternary ammonium salt” means that a nitrogen atom of the amine functionality is covalently bonded to four organic groups and is associated with an anion. These cationic derivatives can be synthesized by functionalizing the monomer before polymerization or by functionalizing the polymer after polymerization. These cationic ethylenically unsaturated monomers include, but are not limited to, N,N dialkylaminoalkyl(meth)acrylate, N-alkylaminoalkyl(meth)acrylate, N,N dialkylaminoalkyl(meth)acrylamide and N-alkylaminoalkyl(meth)acrylamide, where the alkyl groups are independently C₁₋₁₈ aliphatic, cycloaliphatic, aromatic, or alkyl aromatic and the like. Aromatic amine containing monomers such as vinyl pyridine and vinyl imidazole may also be used. Furthermore, monomers such as vinyl formamide, vinyl acetamide and the like which generate amine moieties on hydrolysis may also be used. Preferably the cationic ethylenically unsaturated monomer is N,N-dimethylaminoethyl methacrylate, tert-butylaminoethylmethacrylate and N,N-dimethylaminopropyl methacrylamide.

Cationic ethylenically unsaturated monomers that may be used are the quaternized derivatives of the above monomers as well as diallyldimethylammonium chloride also known as dimethyldiallylammonium chloride, (meth)acrylamidopropyl trimethylammonium chloride, 2-(meth)acryloyloxy ethyl trimethyl ammonium chloride, 2-(meth)acryloyloxy ethyl trimethyl ammonium methyl sulfate, 2-(meth)acryloyloxyethyltrimethyl ammonium chloride, N,N-Dimethylaminoethyl(meth)acrylate methyl chloride quaternary, methacryloyloxy ethyl betaine as well as other betaines and sulfobetaines, 2-(meth)acryloyloxy ethyl dimethyl ammonium hydrochloride, 3-(meth)acryloyloxy ethyl dimethyl ammonium hydroacetate, 2-(meth)acryloyloxy ethyl dimethyl cetyl ammonium chloride, 2-(meth)acryloyloxy ethyl diphenyl ammonium chloride and others.

As used herein, the term “nonionic ethylenically unsaturated monomer” means an ethylenically unsaturated monomer which does not introduce a charge in to the non-anionic hybrid mixture. These nonionic ethylenically unsaturated monomers include, but are not limited to, acrylamide, methacrylamide, N alkyl(meth)acrylamide, N,N dialkyl(meth)acrylamide such as N,N dimethylacrylamide, hydroxyalkyl(meth)acrylates, alkyl(meth)acrylates such as methylacrylate and methylmethacrylate, vinyl acetate, vinyl morpholine, vinyl pyrrolidone, vinyl caprolactam, vinyl formamide, vinyl acetamide, ethoxylated alkyl, alkaryl or aryl monomers such as methoxypolyethylene glycol(meth)acrylate, allyl glycidyl ether, allyl alcohol, glycerol(meth)acrylate, monomers containing silane, silanol and siloxane functionalities and others. The nonionic ethylenically unsaturated monomer is preferably water soluble. The preferred nonionic ethylenically unsaturated monomers are acrylamide, methacrylamide, N methyl(meth)acrylamide, N,N dimethyl(meth)acrylamide, vinyl pyrrolidone, vinyl formamide, vinyl acetamide and vinyl caprolactam.

The cationic or non-ionic hybrid mixture has a naturally derived hydroxyl containing chain transfer agent. The chain transfer agent is preferably present from about 0.1% by weight to about 98%, more preferably from about 10 to about 95% and most preferably from about 20 to about 75% by weight, based on the total weight of the cationic or non-ionic hybrid copolymer composition. In another embodiment, the chain transfer agent is preferably present from about 40% to about 60% by weight. In an embodiment, the chain transfer agent may be the terminating moiety, or end group of the polymeric chain comprised of the ethylenically unsaturated monomer.

Hybrid mixtures useful in gas hydrate inhibitor compositions include both anionic and non-anionic intimate mixtures and/or hybrid copolymer compositions. In an embodiment, a gas hydrate inhibitor composition includes at least one nonionic ethylenically unsaturated monomer which is a vinyl lactam or vinyl lactam with a co-monomer, such as a non-anionionic co-monomer. In a further embodiment, the at least one nonionic ethylenically unsaturated monomer is N-vinyl pyrrolidone or vinyl caprolactam or combinations thereof. In an embodiment, the nonionic ethylenically unsaturated monomer is -a combination of vinyl pyrrolidone or vinyl caprolactam present in a ratio in a range of from about 25:75 to about 75:25 vinyl pyrrolidone to vinyl caprolactam.

In yet another embodiment, the gas hydrate inhibitor composition includes a naturally derived hydroxyl containing chain transfer agent which is a polysaccharide. In a further embodiment, the polysaccharide can be hydrolyzed starch having a DE of greater than 5. In an even further embodiment, the polysaccharide is maltodextrin having a DE greater than 5. In an embodiment of the invention, the maltodextrin has a DE of 10 or greater.

In a further embodiment, the naturally derived hydroxyl containing chain transfer agent comprises maltodextrin or corn syrup solids. In an embodiment of the invention, the maltodextrin or corn syrup solids, preferably has a dextrose equivalent (DE) of greater than 5. In another embodiment, the maltodextrin or corn syrup solids has a DE of 10 or greater. The term dextrose equivalent, as used herein, is a measure of the amount of reducing sugars present in a sugar product, relative to glucose, and is a well known term of art.

In another embodiment, the hybrid copolymer composition and/or intimate mixture is made in the presence of a hybrid initiator. “Hybrid initiators”, for purposes of this invention, include free radical initiators, initiating systems excluding metal ion based initiators or metal ion-based initiators.

In an embodiment, the hybrid initiators are free radical initiators or initiating systems excluding metal ion based initiators or initiating systems. The hybrid initiators preferably are not free radical abstractors but promote chain transfer. Furthermore, the hybrid initiator is preferably water soluble. Exemplary hybrid initiators include, but are not limited to, peroxides, azo initiators as well as redox systems like tert-butyl hydroperoxide and erythorbic acid, peroxide such as persulfate and an amine such as hydroxylamine sulfate, persulfate and sodium formaldehyde sulfoxylate etc. The hybrid initiators may include both inorganic and organic peroxides. Suitable inorganic peroxides include sodium persulfate, potassium persulfate and ammonium persulfate. Azo initiators, such as water soluble azo initiators, may also be suitable hybrid initiators. Water soluble azo initiators include, but are not limited to, 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2′-Azobis(2-methylpropionamidine)dihydrochloride, 2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2′-Azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride, 2,2′-Azobis[2-(2-imidazolin-2-yl)propane], 2,2′-Azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride, 2,2′-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethl]propionamide}, 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and the like.

In an embodiment, the initiator is a nonionic initiator. Exemplary hybrid initiators include, but are not limited to, peroxides, azo initiators as well as redox systems like tert-butyl hydroperoxide and erythorbic acid, peroxide such as persulfate and an amine such as hydroxylamine sulfate, persulfate and sodium formaldehyde sulfoxylate etc. In an embodiment of the invention, the initiator is an Azo initiator, such as 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] or 2,2′-Azobis(2-methylpropionamidine)dihydrochloride.

In embodiment, the hybrid mixtures utilized as gas hydrate inhibitors in accordance with the present invention may be used either in pure aqueous solution or alternatively in solvent mixtures, such as in water/alcohol mixtures. A suitable solvent may include ethylene glycol. In another embodiment, the hybrid mixtures may be made into powders by removing the solvent and drying. Accordingly, the hybrid mixtures may be redispersed or redissolved by introducing the powdered mixtures into the water-containing media in which gas hydrate formation occurs. In an embodiment, the hybrid mixtures are added to the liquid systems, such as mineral oil mixtures or natural gas mixtures, in an amount which one of ordinary skill in the art would select based on the particular application and conditions. In embodiments of the invention, the hybrid mixtures are hybrid copolymer compositions encompassing both anionic and non-anionic hybrid copolymer compositions which are latently-detectable, which means that they will not be detectable in the visible light range until the hybrid copolymer composition is contacted with a photoactivator. As defined herein, the “photoactivator” is an appropriate reagent or reagents which, when present in effective amounts, will react with the hybrid copolymer composition, thereby converting the hybrid copolymer composition into a chemical species which strongly absorbs in the region from about 300 to about 800 nanometers when activated with, for example, sulfuric acid and phenol. In an embodiment of this invention, the activated hybrid copolymer composition will absorb in the region from about 400 to about 700 nanometers.

A latently detectable moiety of this invention will be formed from a naturally derived hydroxyl containing chain transfer agent especially when it is saccharide or polysaccharide moiety. The photoactivator may be the combination of sulfuric acid and phenol (see Dubois et al, Anal. Chem. 28 (1956) p. 350 and Example 1 of U.S. Pat. No. 5,654,198, which is incorporated in its entirety by reference herein). Polymers typically tagged with latently detectable moieties exhibit a drop in efficacy when compared to polymers without these groups. This is especially true when the weight percent of the latently detectable moiety is over 10 or 20 percent of the polymer. However, it has been found that the hybrid copolymers compositions of the present invention perform well even when containing 50 percent or more of the latently detectable moiety. Thus, the advantages of good performance and ready detectability are provided, which allow monitoring the system and controlling scale without over dosing the scale control polymer.

In further embodiments of the present invention, the ethylenically unsaturated monomer of the hybrid mixture may optionally be selected from at least one ester monomer.

Exemplary ester monomers include, but are not limited to, esters derived from dicarboxylic acid as well as hydroxyalkyl esters. Suitable ester monomers derived from dicarboxylic acid include, but are not limited to, monomethylmaleate, dimethylmaleate, monomethylitaconate, dimethylitaconate, monoethylmaleate, diethylmaleate, monoethylitaconate, diethylitaconate, monobutylmaleate, dibutylmaleate, monobutylitaconate and dibutylitaconate. Suitable hydroxyalkyl esters include, but are not limited to, hydroxy ethyl(meth)acrylate, hydroxy propyl(meth)acrylate, hydroxy butyl(meth)acrylate and the like.

In still yet another aspect, the invention relates to an “amphoteric hybrid mixture” containing both anionic and cationic groups. The anionic moieties can be on the natural component with the cationic moieties on the synthetic component or the cationic moieties can be on the natural component with the anionic moieties on the synthetic component or combinations thereof. In an embodiment, for example when the natural component is a polysaccharide, the anionic material can be an oxidized starch and the cationic moiety can be derived from cationic ethylenically unsaturated monomers such as diallyldimethylammonium chloride. Alternatively, the oxidized starch itself may first be reacted with cationic substituent such as 3-chloro-2-hydroxypropyl)trimethylammonium chloride and then reacted with a synthetic anionic or cationic monomer or mixtures thereof.

In another embodiment, a cationic starch may be reacted with an anionic monomer. Finally, the cationic and anionic moieties may be on the synthetic component of these polymers. These amphoteric hybrid copolymer composition containing both anionic and cationic groups are particularly useful in detergent formulations as dispersants and cleaning aids. It is understood that these polymers will contain both a natural component and a synthetic component. The cationic moieties are preferably present in the range of 0.001 to 40 mole % of the anionic moieties, more preferably the cationic moieties are present in the range of 0.01 to 20 mole % of the anionic moieties, and most preferably the cationic moieties are present in the range of 0.1 to 10 mole % of the anionic moieties.

Polymers formed from cationic ethylenically unsaturated monomers generally tend to have poorer toxicological and environmental profiles compared to polymers formed from non-cationic ethylenically unsaturated monomers. Therefore, it may be necessary to minimize the level of cationic ethylenically unsaturated monomer used in preparing the amphoteric hybrid mixture. In an embodiment of the invention, when a cationic ethylenically unsaturated monomer is used to produce an amphoteric hybrid mixture, the cationic ethylenically unsaturated monomer is preferably present up to 10 mole % of the hybrid mixture, more preferably the cationic ethylenically unsaturated monomer is preferably present up to 6 mole % of the hybrid mixture, and most preferably the cationic ethylenically unsaturated monomer is preferably present up to 5 mole % of the hybrid mixture.

In still yet another aspect, the invention relates to hybrid mixtures derived from monomers produced from natural sources such as acrylamide produced by fermentation. One skilled in the art will recognize that monomers produced from natural sources increase the renewable carbon content of the polymers of this invention.

EXAMPLES

The following examples are intended to exemplify the present invention but are not intended to limit the scope of the invention in any way. The breadth and scope of the invention are to be limited solely by the claims appended hereto.

Synthesis Example 1 Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 9.0-12.0) Hybrid Mixture by Synthesis Method A

This is an example of a successful synthesis. The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 9.0-12.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 9.0-12.0 roughly corresponds to a glucose degree of polymerization of 10-13, or a number average molecular weight (Mn) of 1600-2100. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A critical feature of this synthesis is that a maltodextrin with a DE>5 was used.

Reagents: Initial Charge:

Deionized water 23.5671 g Maltrin M100 (Grain Processing Corporation; 26.4966 g, Lot# M0910530; 94.41% solids) as is basis; 25.0154 g, 100% basis N-vinyl pyrrolidone (Aldrich)  6.2436 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]  0.0654 g (Wako VA-086)

Addition Funnel #1:

2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]  0.1908 g (Wako VA-086) Deionized water 55.2253 g

Addition Funnel #2:

N-vinyl pyrrolidone (Aldrich) 18.7925 g Deionized water 36.9796 g

A four-neck round bottom flask was equipped with a mechanical stirrer, reflux condenser, a 60 mL addition funnel and a 125 mL addition funnel. The weight of the flask with stirring apparatus alone was 483.20 g. To the flask were charged 23.5671 g deionized water and 26.4966 g Maltrin M100 maltodextrin. The mixture was stirred until a homogeneous solution was obtained.

To the 60 mL addition funnel was charged a solution of VA-086 initiator in deionized water (Additional Funnel #1); to the 125 mL addition funnel was charged a solution of N-vinyl pyrrolidone in deionized water [Addition Funnel #2].

The reaction was warmed to 95° C. using a thermostatted oil bath. When the temperature reached about 53° C., 6.2436 g N-vinyl pyrrolidone and 0.0654 g VA-086 were added in one portion and heating was continued. A transient light pink color was noted after the addition; the mixture remained clear. When temperature reached 93° C., drop-wise addition over 2.45 h of the contents of the two addition funnels was commenced. The rate of addition was fairly uniform although adjustments to the rate were occasionally necessary to keep the addition rates even. After the addition was complete, heating at 95° C. was continued for an additional 2.75 h. At the conclusion of the reaction, the polymer solution was clear.

After cooling and standing overnight, the polymer solution was turbid and phase separation appeared to have occurred. The polymer was diluted in the reaction vessel with a total of 83.3 g deionized water. A clear, apparently single phase solution was obtained. The yield of polymer solution measured in the flask was 246.08 g.

Theoretical solids of the polymer solution (based on the amount of monomer and maltodextrin added divided by the total yield of polymer solution): 20.3%. The experimental solids (gravimetric at 130° C. for 1.5 h, duplicate runs) was 19.9%. This corresponds to a monomer conversion of 96%.

Synthesis Example 2 Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 9.0-12.0) Hybrid Mixture by Synthesis Method B

This is an example of a successful synthesis. The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 9.0-12.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 9.0-12.0 roughly corresponds to a glucose degree of polymerization of 10-13, or a number average molecular weight (Mn) of 1600-2100. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A critical feature of this synthesis is that a maltodextrin with a DE>5 was used.

Reagents: Initial Charge:

Deionized water  14.49 g N-vinyl pyrrolidone (Aldrich)  6.29 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] 0.0624 g (Wako VA-086)

Addition Funnel #1:

Maltrin M100 (Grain Processing Corporation; Lot# M0910530; 26.4923 g, 94.41% solids) as is basis; 25.0114 g, 100% basis 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]  0.1888 g (Wako VA-086) Deionized water  46.51 g

Addition Funnel #2:

N-vinyl pyrrolidone (Aldrich) 18.7547 g Deionized water 54.5410 g

A four-neck round bottom flask was equipped with a mechanical stirrer, reflux condenser, and two 125 mL addition funnels. The weight of the flask with stirring apparatus alone was 479.19 g. To the flask were charged 14.49 g deionized water, 6.29 g N-vinyl pyrrolidone, and 0.0624 g Wako VA-086. The mixture was stirred until a homogeneous solution was obtained.

To the first 125 mL addition funnel was charged a solution of 0.1888 g VA-086 initiator and 26.4923 g Maltrin M100 in 46.51 g deionized water [Additional Funnel #1]; to the second 125 mL addition funnel was charged a solution of N-vinyl pyrrolidone in deionized water [Addition Funnel #2].

The reaction was warmed to 95° C. using a thermostatted oil bath. When temperature reached 93° C., drop-wise addition over 3 h of the contents of the two addition funnels was commenced. The rate of addition was fairly uniform although adjustments to the rate were occasionally necessary to keep the addition rates even. After the addition was complete, heating at 95° C. was continued for an additional 3 h. At the conclusion of the reaction, the polymer solution was clear.

After cooling and standing overnight, the polymer solution was turbid and phase separation appeared to have occurred. The polymer was diluted in the reaction vessel with a total of 83.3 g deionized water. A clear, apparently single phase solution was obtained. The yield of polymer solution measured in the flask was 249.24 g.

Theoretical solids of the polymer solution (based on the amount of monomer and maltodextrin added divided by the total yield of polymer solution): 20.1%. The experimental solids (gravimetric at 130° C. for 1.5 h) was 20.1%. This corresponds to a monomer conversion of essentially 100%.

Synthesis Examples 3-8 Preparation of Additional Non-Ionic Hybrid Mixtures

Additional hybrid copolymer compositions were prepared by Synthesis Methods A or B. The compositions are summarized in Table 1 below.

TABLE 1 Additional hybrid copolymer compositions. Amount of maltodextrin in final polymer Polymer Synthesis Synthetic (wt.% of dry concentration in Example Method Maltodextrin used component polymer) water 3 B Maltrin M100 N-vinyl 35 wt. % 28.9 wt. % (DE 9.0-12.0) pyrrolidone 4 B Maltrin M100 N-vinyl 65 wt. % 29.7 wt. % (DE 9.0-12.0) pyrrolidone 5 A Maltrin M100 N-vinyl 50 wt. % 36.3 wt. % (DE 9.0-12.0) pyrrolidone (50 wt %) and vinyl caprolactam (50 wt. %) 6 B Maltrin M150 N-vinyl 50 wt. % 25.1 wt. % (DE 13.0-17.0) pyrrolidone 7 A Maltrin M100 N-vinyl 90 wt. % 29.9 wt. % (9.0-12.0) pyrrolidone 8 A Maltrin M150 N-vinyl 50 wt. % 28.7 wt. % (DE 13.0-17.0)) pyrrolidone( 75 wt. %), methacrylamide (20 wt. %); and vinyl imidazole (5 wt. %)

All of the resulting polymers were clear in solution at the listed concentration in water. The polymer solutions were preserved by the addition of 0.5-0.75 wt % Glydant Plus.

Synthesis Example 9 Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 9.0-12.0) Hybrid Mixture by Synthesis Method C

This is an example of a successful synthesis. The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 9.0-12.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 9.0-12.0 roughly corresponds to a glucose degree of polymerization of 10-13, or a number average molecular weight (Mn) of 1600-2100. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A critical feature of this synthesis is that a maltodextrin with a DE>5 was used.

Reagents: Initial Charge:

Deionized water 288.75 g Maltrin M100 (DE 9.0-12.0; Grain Processing Corporation;  66.45 g, 94.05% solids) as is basis;  62.50 g, 100% basis N-vinyl pyrrolidone (Aldrich)  62.5 g 2,2'-Azobisisobutyronitrile (Vazo 64; DuPont)  0.63 g

1 L four-neck round bottom reaction flask was equipped with a 2¾″ S-S mechanical stirrer/overhead mixer motor, thermometer and nitrogen inlet topped reflux condenser. To the flask was charged 62.5 g N-vinyl pyrrolidone and 0.63 g Vazo-64 initiator. The resulting solution was purged with with nitrogen at ambient temperature for about 15 minutes.

To a 600 mL beaker, was add 288.75 g water and 66.45 g Maltrin M100 (Maltodextrin DE=9 to 12; 94.05% solids). The resulting mixture was stirred until the maltodextrin dissolved, and then the clear maltodextrin solution was transferred to a 500 mL addition funnel. The addition funnel was set up on reactor, and a sub-surface nitrogen purge was applied to the solution in the addition funnel at ambient temperature for about 15 minutes.

The maltodextrin solution was added rapidly to the reaction flask monomer/initiator in reactor. Heating of the reaction mixture was then begun using a water bath (hot-plate controlled by Thermo-watch controlled via bath thermometer). The reaction temperature was brought to 70±1° C.° under a positive pressure of nitrogen. A≈3° C. exotherm was noted during the initial ¾ Hr of reaction, after which the reaction and bath temperatures became almost equal.

The reaction was held at 70° C. for a total of 10 h (over two days). At the conclusion of the polymerization, the reaction was cooled to ambient temperature with a cold water bath, the amount of water that was found to be lost (2.18 g) was replenished.

The polymer solution as prepared was not transparent. The polymer solution was diluted from 30.3% solids (in theory) to 20% solids (in theory by the addition of water, but the solution was still not clear. Further dilution to a theoretical polymer concentration of 18 wt. % resulted in an essentially transparent solution. A total of 279.58g extra water was needed to dilute the polymer.

The yield of polymer solution was 697.9 g. The experimental solids was 17.9%. This corresponds to a monomer conversion of 99.4. The final product was preserved by the addition of 0.75 wt % Glydant Plus on total solution weight; final polymer solution solids were 18.47%.

Synthesis Example 10 Synthesis of Non-Ionic Hybrid Mixture with Polysaccharide Chain Transfer Agent

50 grams of maltodextrin as a polysaccharide chain transfer agent (STAR-DRI 180 DE 18 spray-dried maltodextrin available from Tate and Lyle, Decatur, Ill.) was dissolved in 150 grams of water in a reactor and heated to 75° C. A monomer solution containing 50 grams of hydroxyethylacrylate was subsequently added to the reactor over a period of 50 minutes. An initiator solution comprising of 2 grams of V-50 [2,2′-Azobis(2 amidino-propane)dihydrochloride azo initiator from Wako Pure Chemical Industries, Ltd., Richmond, Va.] in 30 grams of water was added to the reactor at the same time as the monomer solution over a period of 60 minutes. The reaction product was held at 75° C. for an additional 60 minutes. The final product was a clear almost water white solution.

Synthesis Example 11 Synthesis of Non-Anionic Hybrid Mixture

150 grams of maltodextrin as a polysaccharide chain transfer agent (Cargill MD™ 01918 dextrin, spray-dried maltodextrin obtained by enzymatic conversion of common corn starch, available from Cargill Inc., Cedar Rapids, Iowa) was initially dissolved in 200 grams of water in a reactor and 70 g of HCl (37%) was added and heated to 98° C. A monomer solution containing 109 grams of dimethyl aminoethyl methacrylate dissolved in 160 grams of water was subsequently added to the reactor over a period of 90 minutes. An initiator solution comprising of 6.6 grams of sodium persulfate in 40 grams of water was added to the reactor at the same time as the monomer solution over a period of 90 minutes. The reaction product was held at 98° C. for an additional 60 minutes. The reaction product was then neutralized by adding 14 grams of a 50% solution of NaOH and the final product was an amber colored solution.

Synthesis Example 12 Synthesis of Non-Anionic Hybrid Mixture

35 grams of Amioca Starch was dispersed in 88 grams of water in a reactor and heated to 52. The starch was depolymerized by addition of 1.07 grams of concentrated sulfuric acid (98%). The suspension was held at 52° C. for 1.5 hours. The reaction was then neutralized with 1.84 grams of 50% NaOH solution and the temperature was raised to 90° C. for 15 minutes. The starch gelatinizes and the viscosity increased during the process and a gel is formed. The viscosity dropped after the gelatinization was completed. The temperature was lowered to 72 to 75° C. A solution of 80.7 grams of dimethyl diallyl ammonium chloride (62% in water) was added to the reactor over a period of 30 minutes. An initiator solution comprising of 0.2 grams of sodium persulfate in 20 grams of water was added to the reactor at the same time as the monomer solution over a period of 35 minutes. The reaction product was held at 98° C. for an additional 2 hours. The final product was a slightly opaque yellow colored solution.

Synthesis Example 13 Synthesis of Non-Anionic Hybrid Mixture

35 grams of Amioca Starch was dispersed in 88 grams of water in a reactor and heated to 52. The starch was depolymerized by addition of 0.52 grams of concentrated sulfuric acid (98%). This is half the acid used in Example 32 and causes less depolymerization of the starch resulting in a higher molecular weight. Thus the molecular weight of the polysaccharide chain transfer agent can be controlled. The suspension was held at 52° C. for 1.5 hours. The reaction was then neutralized with 0.92 grams of 50% NaOH solution and the temperature was raised to 90° C. for 15 minutes. The starch gelatinizes and the viscosity increased during the process and a gel was formed. The viscosity dropped after the gelatinization was completed. The reaction was diluted with 30 grams of water and the temperature was lowered to 72 to 75° C. A solution of 80.7 grams of dimethyl diallyl ammonium chloride (62% in water) was added to the reactor over a period of 30 minutes. An initiator solution comprising of 0.2 grams of sodium persulfate in 20 grams of water was added to the reactor at the same time as the monomer solution over a period of 35 minutes. The reaction product was held at 98° C. for an additional 2 hours. The final product was a clear light yellow colored solution.

Synthesis Example 14 Synthesis of Hybrid Mixture with Polysaccharide (Inulin) Chain Transfer Agent

50 grams of a polysaccharide chain transfer agent (DEQUEST® PB11620 carboxymethyl inulin 20% solution available from Thermphos) was dissolved in 150 grams of water in a reactor and heated to 75° C. A monomer solution containing 50 grams of N,N dimethyl acrylamide was subsequently added to the reactor over a period of 50 minutes. An initiator solution comprising of 2 grams of V-50 [2,2′-azobis(2-amidinopropane)dihydrochloride]azo initiator from Wako Pure Chemical Industries, Ltd., Richmond, Va.] in 30 grams of water was added to the reactor at the same time as the monomer solution over a period of 60 minutes. The reaction product was held at 75° C. for an additional 60 minutes. The reaction product was diluted with 140 grams of water and the final product was a clear homogenous amber colored solution.

Synthesis Example 15 Synthesis of Hybrid Mixture with Polysaccharide (Cellulosic) Chain Transfer Agent

Carboxymethyl cellulose (AQUALON® CMC 9M3ICT available from Hercules, Inc., Wilmington, Del.) was depolymerized in the following manner. Thirty grams of AQUALON® CMC was introduced in to 270 g of deionized water with stirring. 0.03 g of Ferrous ammonium sulfate hexahydrate and 2 g of hydrogen peroxide (H₂O₂) solution (35% active) was added. The mixture was heated to 60° C. and held at that temperature for 30 minutes. This depolymerized CMC solution was then heated to 90° C.

A monomer solution containing 50 grams of acrylamide (50% solution) is subsequently added to the reactor over a period of 50 minutes. An initiator solution comprising of 2 grams of V-086 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]azo initiator from Wako Pure Chemical Industries, Ltd., Richmond, Va.] in 30 grams of water is added to the reactor at the same time as the monomer solution over a period of 60 minutes. The reaction product is held at 90° C. for an additional 60 minutes.

Synthesis Example 16 Synthesis of a Non-Anionic Hybrid Mixture Containing a Quaternary Amine Monomer and a Cationic Polysaccharide Functionality

40 grams of Nsight C-1 as a cationic starch chain transfer agent (available from AkzoNobel, Bridgewater N.J.) was initially dissolved in 100 grams of water in a reactor and heated to 98° C. A solution of 38.7 grams of dimethyl diallyl ammonium chloride (62% in water) was subsequently added to the reactor over a period of 45 minutes. An initiator solution comprising of 3.3 grams of sodium persulfate in 20 grams of water was added to the reactor at the same time as the monomer solution over a period of 45 minutes. The reaction product was held at 98° C. for an additional 60 minutes. The final product was a clear amber colored solution.

Synthesis Example 17 Synthesis of Non-Anionic Hybrid Mixture

35 grams of Hylon VII Starch (a high amylose starch containing 70% amylose) was dispersed in 132 grams of water in a reactor and heated to 52° C. The starch was depolymerized by addition of 1.07 grams of concentrated sulfuric acid (98%). The suspension was held at 52° C. for 1.5 hours. The reaction was then neutralized with 1.84 grams of 50% NaOH solution and the temperature was raised to 90° C. for 15 minutes. The starch gelatinizes and the viscosity increased during the process and a gel was formed. The viscosity dropped after the gelatinization was completed. The reaction was diluted with 30 grams of water and the temperature was lowered to 72 to 75° C. A solution of 100.1 grams of [3-(methacryloylamino)propyl]-trimethylammonium chloride (50% in water) was added to the reactor over a period of 30 minutes. An initiator solution comprising of 0.2 grams of sodium persulfate in 20 grams of water was added to the reactor at the same time as the monomer solution over a period of 35 minutes. The reaction product was held at 98° C. for an additional 2 hours. The final product was an opaque white homogenous solution.

Synthesis Example 18 Synthesis of Non-Anionic Hybrid Mixture

35 grams of Amioca Starch was dispersed in 88 grams of water in a reactor and heated to 52. The starch was depolymerized by addition of 0.52 grams of concentrated sulfuric acid (98%). This is half the acid used in Example 41 and causes less depolymerization of the starch resulting in a higher molecular weight. Thus the molecular weight of the polysaccharide chain transfer agent can be controlled. The suspension was held at 52° C. for 1.5 hours. The reaction was then neutralized with 0.92 grams of 50% NaOH solution and the temperature was raised to 90° C. for 15 minutes. The starch gelatinizes and the viscosity increased during the process and a gel was formed. The viscosity dropped after the gelatinization was completed. The reaction was diluted with 30 grams of water and the temperature was lowered to 72 to 75° C. A solution of 66.71 g [2-(methacryloxy)ethyl]-trimethylammonium chloride (75% in water) was added to the reactor over a period of 30 minutes. An initiator solution comprising of 0.2 grams of sodium persulfate in 20 grams of water was added to the reactor at the same time as the monomer solution over a period of 35 minutes. The reaction product was held at 98° C. for an additional 2 hours. The final product was a homogeneous opaque white paste.

Synthesis Example 19 Synthesis of Non-Ionic Hybrid Mixture with Polysaccharide Chain Transfer Agent

Hydroxyethyl cellulose (QP 300 available from Dow) was depolymerized in the following manner. Thirty grams of QP 300 was introduced in to 270 g of deionized water with stirring. 0.05 g of Ferrous ammonium sulfate hexahydrate and 1 g of hydrogen peroxide (H₂O₂) solution (35% active) was added. The mixture was heated to 60° C. and held at that temperature for 30 minutes. This depolymerized CMC solution was then heated to 90° C.

A solution of 38.7 grams of dimethyl diallyl ammonium chloride (62% in water) is subsequently added to the reactor over a period of 50 minutes. An initiator solution comprising of 2 grams of V-086 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]azo initiator from Wako Pure Chemical Industries, Ltd., Richmond, Va.] in 30 grams of water is added to the reactor at the same time as the monomer solution over a period of 60 minutes. The reaction product is held at 90° C. for an additional 60 minutes.

Synthesis Example 20 Synthesis of Catanionic Hybrid Mixture Containing Both Anionic and Cationic Groups

150 grams of water was added to 765 grams of RediBond 5330A (available from National Starch and Chemical) (27% aqueous solution), and the solution was heated to 40° C. The pH of the solution was adjusted to pH 7.0 with 50% sodium hydroxide solution. 0.13 grams of alpha-amylase was added to the solution, which was allowed to cook for 1 hour. 254.7 grams of this pre-digested RediBond 5330A as a cationic polysaccharide chain transfer agent, 2.32 grams of 50% sodium hydroxide solution, and 20.16 grams of monomethyl maleate was heated in a reactor to 87° C. A monomer solution containing 73.88 grams of acrylic acid and 17.96 grams of water was subsequently added to the reactor over a period of 4.5 hours. An initiator solution comprised of 13.84 grams of erythorbic acid dissolved in 100 grams of water, and a second initiator solution comprised of 13.98 grams of tert-butyl hydrogen peroxide were added to the reactor at the same time as the monomer solution over a period of 5 hours. The reaction product was cooled and held at 65° C. for an additional 60 minutes. The final product was a brown solution.

Synthesis Example 21 Synthesis of an Ester Hybrid Mixture

45.9 grams of monomethylmaleate (ester monomer) was dissolved in 388 grams of water. 15.3 grams of ammonium hydroxide was added and the mixture was heated to 87 C. 85 grams of maltodextrin of DE 18(Cargill MD™ 01918, spray-dried maltodextrin obtained by enzymatic conversion of common corn starch, available from Cargill Inc., Cedar Rapids, Iowa) was added just before the monomer and initiator feeds were started. A monomer solution containing a mixture of 168 grams of acrylic acid and 41.0 grams of hydroxyethyl methacrylate (ester monomer) was added to the reactor over a period of 5 hours. A first initiator solution comprising of 21 grams of erythorbic acid dissolved in 99 grams of water was added over a period of 5.5 hours. A second initiator solution comprising of 21 grams of a 70% solution of tertiary butyl hydroperoxide dissolved in 109 grams of water was added over a period of 5.5 hours. The reaction product was held at 87° C. for 30 minutes. The final product was a clear light amber solution and had 34.1% solids.

Synthesis Example 22 Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 13.0-17.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 13.0-17.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 13.0-17.0 roughly corresponds to a glucose degree of polymerization of 7-9, or a number average molecular weight (Mn) of 1100-1500. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A maltodextrin with a DE>5 was used.

Reagents: Flask:

Deionized water 57.12 g Maltrin M150 (Grain Processing 63.76 g, as is basis; Corporation; Lot# M0905132; 60.03 g, 100% basis 94.15% solids)

Addition Funnel:

N-vinyl pyrrolidone (Aldrich)  60.01 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] 0.6046 g (Wako VA-086) Deionized water 135.07 g

A four-neck 1000 mL round bottom flask was equipped with a mechanical stirrer, reflux condenser, a 250 mL addition funnel, and a stopper. To the flask were charged 57.12 g deionized water and 63.76 g Maltrin M150 maltodextrin. The mixture was stirred until a homogeneous solution was obtained. To the 250 mL addition funnel was charged a solution of 60.01 g N-vinyl pyrrolidone and 0.6046 g VA-086 in deionized water.

The reaction was warmed to 80° C. using an oil bath and ¼ of the contents of the addition funnel were added at once. Heating was continued, and when the temperature reached 95° C., drop-wise addition at a uniform rate over 3 h. of the contents of the addition funnel was commenced. After the addition was complete, heating at 95° C. was continued for an additional 2.75 h. At the conclusion of the reaction, the polymer solution was clear with some viscosity build.

After cooling and standing overnight, the polymer solution was turbid and phase separation appeared to have occurred. The reaction mixture was then heated for 1 h. at >95° C. and then diluted in the reaction vessel with a total of 88.62 g deionized water. A clear, apparently single phase solution was obtained. The yield of polymer solution measured in the flask was 400.0 g. The experimental solids (gravimetric at 130° C. for 1.5 h, duplicate runs) was 30.4%.

The polymer was preserved by the addition of 0.75 wt. % Glydant Plus.

Synthesis Example 23 Preparation of an N-vinyl pyrrolidone-co-vinyl caprolactam/maltodextrin (DE 13.0-17.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from a combination of N-vinyl pyrrolidone and vinyl caprolactam; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 13.0-17.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 13.0-17.0 roughly corresponds to a glucose degree of polymerization of 7-9, or a number average molecular weight (Mn) of 1100-1500. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A maltodextrin with a DE>5 was used.

Reagents: Flask:

Deionized water 56.48 g Maltrin M150 (Grain Processing 63.72 g, as is basis; Corporation; Lot# M0905132; 59.99 g, 100% basis 94.15% solids)

Addition Funnel #1:

N-vinyl pyrrolidone (Aldrich) 30.05 g N-vinyl caprolactam (Aldrich) 30.41 g

Addition Funnel #2:

Deionized water 135.00 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] 0.6085 g (Wako VA-086)

A four-neck round 1000 mL bottom flask was equipped with a mechanical stirrer, reflux condenser, 125 mL addition funnel, and a 250 mL addition funnel. To the flask were charged 56.48 g deionized water and 63.72 g maltodextrin Maltrin M150 (DE 13.0-17.0). The mixture was stirred with gentle heating until a homogeneous solution was obtained.

Addition Funnel #1 was charged with a mixture of 30.05 g N-vinyl pyrrolidone and 30.41 g N-vinyl caprolactam (homogeneous solution). Addition Funnel #2 was charged with a solution of 0.6085 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (Wako VA-086) in 135.00 g deionized water.

The reaction was warmed to about 75° C. using a thermostatted oil bath. At this point, ¼ of the contents of each addition funnel was added at once. The solution in the flask became cloudy—it was no longer homogeneous. Heating of the reaction vessel was continued, and when the reaction temperature reached 96° C., drop-wise addition of the contents of the two addition funnels over a period of 3 h. was commenced. The rate of addition was fairly uniform although adjustments to the rate were occasionally necessary to stay on target for a 3 h. addition time; the reaction temperature was maintained at 96-99° C. throughout the polymerization. The reaction mixture remained cloudy throughout the polymerization, and there appeared to be a formation of distinct phases. After the addition was complete, heating was continued for an additional 0.5 h. At the conclusion of the reaction, the polymer solution was cloudy.

After cooling and standing overnight, the polymer solution had become clear and apparently homogeneous, and it was somewhat viscous. The reaction mixture was heated to 95-100° C. for an additional 3.5 h. On heating, the reaction mixture again became cloudy. On cooling, the reaction mixture clarified. The temperature at which the mixture clarified was about 68° C. To the clear reaction mixture was then added 10.05 g deionized water. A clear, apparently single phase solution was obtained. The yield of polymer solution measured in the flask was 316.18 g. The experimental solids (gravimetric at 130° C. for 1.5 h; average of two runs) was 37.8%. This corresponds to a monomer conversion of about 98%.

The polymer solution was preserved by the addition of 0.75 wt. % Glydant Plus.

Cloud point at 1 wt. % in water (heating rate ˜2° C./minute): 77° C.

Synthesis Example 24 Preparation of an N-vinyl pyrrolidone-co-vinyl caprolactam/maltodextrin (DE 13.0-17.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from a combination of N-vinyl pyrrolidone and vinyl caprolactam; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 13.0-17.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 13.0-17.0 roughly corresponds to a glucose degree of polymerization of 7-9, or a number average molecular weight (Mn) of 1100-1500. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt % (based on dry polymer). A maltodextrin with a DE>5 was used.

Reagents: Flask:

Deionized water 56.24 g Maltrin M150 (Grain Processing 63.75 g, as is basis; Corporation; Lot# M0905132; 60.02 g, 100% basis 94.15% solids)

Addition Funnel #1:

N-vinyl pyrrolidinone (Aldrich) 33.0594 g N-vinyl caprolactam (Aldrich) 33.0421 g Combined Monomer Mixture 66.1015 g Added to reaction:  60.22 g

Addition Funnel #2:

Deionized water 135.03 g 2,2′-Azobis(2-methylpropionamidine)dihydrochloride 0.6130 g (Wako V-50)

A four-neck round 1000 mL bottom flask was equipped with a mechanical stirrer, a nitrogen inlet topped reflux condenser, 125 mL addition funnel, and a 250 mL addition funnel. To the flask were charged 56.24 g deionized water and 63.75 g maltodextrin Maltrin M150 (DE 13.0-17.0). The mixture was stirred with gentle heating until a homogeneous solution was obtained.

Addition Funnel #1 was charged with 60.22 g of a 50/50 (w/w) mixture of N-vinyl pyrrolidinone and N-vinyl caprolactam (homogeneous solution). Addition Funnel #2 was charged with a solution of 0.6130 g 2,2′-Azobis(2-methylpropionamidine)dihydrochloride (Wako V-50) in 135.03 g deionized water.

The contents of the flask, Addition funnel #1, and Addition Funnel #2 were deoxygenated by sub-surface purging with nitrogen for 15, 5, and 5 minutes, respectively.

The reaction was warmed to about 70° C. using a thermostatted oil. At this point, ¼ of the contents of each addition funnel was added at once. The solution in the flask became hazy—it was no longer homogeneous. Drop-wise addition of the contents of the two addition funnels over a period of 3 h. was then commenced. The rate of addition was fairly uniform although adjustments to the rate were occasionally necessary to stay on target for a 3 h. addition time. The reaction temperature was maintained at 65-71° C. throughout the polymerization, and the polymerization was kept under a positive pressure of nitrogen throughout. The reaction mixture remained cloudy throughout the polymerization, and there appeared to be a formation of distinct phases. After the addition was complete, heating was continued for an additional 3 h. At the conclusion of the reaction, the polymer solution was frothy, white (cloudy), and viscous.

After cooling and standing overnight, the polymer solution had clarified significantly, but it was still slightly turbid. The reaction was diluted to 400 g total by the addition of 90.9 g deionized water, but it did not fully clear. An additional 75.27 g deionized water was added; the reaction was nearly clear at this point and apparently homogeneous. The yield of polymer solution measured in the flask was 475.27 g. The experimental solids (gravimetric at 130° C. for 1.5 h; average of two runs) was 24.9%.

The polymer solution was preserved by the addition of 0.57 wt. % Glydant (solid).

Cloud point at 1 wt. % in water (heating rate ˜2° C./minute) was 58° C.

Synthesis Example 25 Preparation of vinyl caprolactam/maltodextrin (DE 13.0-17.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from vinyl caprolactam; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 13.0-17.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 13.0-17.0 roughly corresponds to a glucose degree of polymerization of 7-9, or a number average molecular weight (Mn) of 1100-1500. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A maltodextrin with a DE>5 was used.

The polymer was prepared according to the method described in Synthesis Example 22 with the following exceptions. 4,4′-Azobis(4-cyanovaleric acid), 0.5 parts per hundred parts monomer and maltodextrin combined(pphm), neutralized to pH 7 with sodium hydroxide, was used as the initiator, and the reaction was post-treated with 0.2 pphm 4,4′-Azobis(4-cyanovaleric acid), neutralized to pH 7 with sodium hydroxide for 5 h at reflux after dilution of polymer solids to 20 wt. %. The yield of homogenous polymer solution was 703.4 g. The solids were 19.1%.

Synthesis Example 26 Preparation of vinyl caprolactam/glucose Hybrid Copolymer

The synthetic component of the hybrid copolymer composition is derived from vinyl caprolactam N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from glucose, which is the naturally derived hydroxyl containing chain transfer agent.

The polymer is prepared according to the method described in Synthesis Example 22.

Synthesis Example 27 Preparation of vinyl caprolactam/lactose Hybrid Copolymer

The synthetic component of the hybrid copolymer composition is derived from vinyl caprolactam N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from lactose, which is the naturally derived hydroxyl containing chain transfer agent.

The polymer is prepared according to the method described in Synthesis Example 22.

Comparative Synthesis Example 1 Attempted Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 4.0-7.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 4.0-7.0maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 4.0-7.0 roughly corresponds to a glucose degree of polymerization of 17 to 30, or a number average molecular weight (Mn) of 2800 to 4900. The amount of the hybrid copolymer composition derived from maltodextrin was 50 wt. % (based on dry polymer). A maltodextrin with a DE of about 5 was used.

Reagents: Initial Charge:

Deionized water  57.12 g Maltrin M040, (DE 4.0 - 7.0 maltodextrin; 26.3804 g, as is basis; Grain Processing Corporation; 94.77% solids) 25.0007 g, 100% basis N-vinyl pyrrolidone (Aldrich)  6.3053 g 2,2′-Azobis[2-methyl-N-(2-  0.0645 g hydroxyethyl)propionamide] (Wako VA-086)

Addition Funnel #1:

2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]  0.1934 g (Wako VA-086) Deionized water 38.9322 g

Addition Funnel #2:

N-vinyl pyrrolidone (Aldrich) 18.7595 g Deionized water 19.8633 g

A four-neck round bottom flask was equipped with a mechanical stirrer, reflux condenser, a 60 mL addition funnel and a 125 mL addition funnel. The weight of the flask with stirring apparatus alone was 467.74 g. To the flask were charged 57.12 g of deionized water and 26.3804 g Maltrin M040. The resulting mixture was heated using a thermostatted oil bath to ˜90° C. at which point the maltodextrin slowly dissolved to give a clear, slightly viscous solution.

To the 60 mL addition funnel was charged a solution of 0.1934 g VA-086 initiator in 38.9322 g deionized water [Additional Funnel #1]; to the 125 mL addition funnel was charged a solution of 18.7595 g N-vinyl pyrrolidone in 19.8633 g deionized water [Addition Funnel #2].

At this point, 6.3053 g N-vinyl pyrrolidone and 0.0645 g Wako VA-086 plus a few mL of deionized water rinses were charged to the reaction mixture and heating was continued. When the reaction temperature reached 93° C., drop-wise addition over 2.5 h of the contents of the two addition funnels was commenced. The rate of addition was fairly uniform although adjustments to the rate were occasionally necessary to keep the addition rates even. The reaction was kept at 95±2° C. for the duration of the addition. Some turbidity was noted towards the end of the monomer/initiator addition. After the addition was complete, heating at 95° C. was continued for an additional 3.25 h. At the conclusion of the reaction, the polymer solution was turbid at 95° C.

Significant phase separation was noted after the polymerization reaction had been allowed to stand overnight; the reaction mixture was white and cloudy. The reaction mixture was heated to about 90° C. for about 20 minutes; at about 76° C., the mixture became translucent. The reaction was diluted with 83.52 g water at elevated temperature and then allowed to cool down. A clear solution was never obtained. Yield of polymer solution measured in the flask: 250.01 g.

Dilution of a small amount of the homogenized mixture to 10% solids failed to give a clear solution.

Theoretical solids of the polymer solution (based on the amount of monomer and maltodextrin added divided by the total yield of polymer solution): 20.0%. The experimental solids (gravimetric at 130° C. for 1.5 h) was 20.0%. This corresponds to a monomer conversion of essentially 100%.

On standing for several days, massive phase separation was noted.

Comparative Synthesis Example 2 Attempted Preparation of an N-vinyl pyrrolidone/maltodextrin (DE 4.0-7.0) Hybrid Mixture

The synthetic component of the hybrid copolymer composition is derived from N-vinyl pyrrolidone; the naturally occurring portion of the hybrid copolymer composition is derived from a DE 4.0-7.0 maltodextrin, which is the naturally derived hydroxyl containing chain transfer agent. A DE of 44.0-7.0 roughly corresponds to a glucose degree of polymerization of 17 to 30, or a number average molecular weight (Mn) of 2800 to 4900. The amount of the hybrid copolymer composition derived from maltodextrin was 25 wt. % (based on dry polymer). A maltodextrin with a DE of about 5 was used.

Reagents: Initial Charge:

Deionized water  28.84 g Maltrin M040 (DE 4.0 - 7.0 maltodextrin; 13.1807 g, as is basis; Grain Processing Corporation; 94.77% solids) 12.4913 g, 100% basis

125 mL Addition Funnel:

N-vinyl pyrrolidone (Aldrich) 37.5242 g 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]  0.3838 g (Wako VA-086) Deionized water 58.2860 g

A four-neck round bottom flask was equipped with a mechanical stirrer, reflux condenser, a 125 mL addition funnel, and a stopper. The weight of the flask with stirring apparatus alone was 471.62 g. To the flask were charged 13.1807 g Maltrin M040 (DE 5 maltodextrin) and 28.84 g deionized water. The mixture was heated to ˜90° C. with stirring until a clear, homogeneous solution was obtained. The mixture was allowed to cool somewhat after it became clear, but it did not drop below 50° C.

To the 125 mL addition funnel was charged a solution of VA-086 initiator and N-vinyl pyrrolidone in deionized water. The volume in the addition funnel was 98 mL. To the reaction mixture was rapidly added 24.5 mL (¼ of the total volume) of the contents of the addition funnel.

The resulting mixture was stirred and warmed to 95° C. using a thermostatted oil bath. When the temperature reached 93° C., drop-wise addition over 3 h of the contents of the addition funnels was commenced. The rate of addition was fairly uniform throughout. During the course of the addition viscosity was noted to increase, and the reaction mixture gradually changed from clear to hazy. After the addition was complete, heating at 95° C. was continued for an additional 3 h. One hour after the addition was complete, 29.17 mL deionized water was added drop-wise to the reaction via the addition funnel while the reaction temperature was maintained at 95° C. The polymerization reaction mixture remained hazy after the addition of the water. After heating was stopped, the reaction became quite turbid.

After cooling and standing overnight, the polymer solution was opaque, but there was no evidence of phase separation. The reaction was heated to ˜90° C. and 83.04 g deionized water was added to further dilute the polymer solution. The polymer solution did not become clear. The yield of product measured in the flask was 245.64 g. An additional 4.26 g of deionized water was added to the reaction vessel. Adjusted yield: 249.9 g.

Theoretical solids of the polymer solution (based on the amount of maltodextrin and N-vinyl pyrrolidone added divided by the total yield of polymer solution): 20.0%. The experimental solids (gravimetric at 130° C. for 1.5 h, duplicate runs) was 20.4%. This corresponds to a monomer conversion of essentially 100%.

A small portion of the product was diluted to 10% solids. This did not clarify the solution.

Product was preserved by the addition of 0.75 wt. % Glydant Plus.

On standing for several days massive phase separation was noted.

Evaluation of Hybrid Polymers

A solution of the polymer to be evaluated was prepared at the desired concentration (based on 100% active polymer) in 50 mL distilled water. This was charged to a 200 mL jacketed stainless steel pressure cell equipped with a blade stirrer. The vessel was pressurized to 77 bar with a synthetic natural gas of the formula given in Table 1.

TABLE 1 Synthetic natural gas composition Amount Component (mole %) Methane 80.67 Ethane 10.20 Propane 4.90 Iso-Butane 1.53 n-Butane 0.76 N₂ 0.10 CO₂ 1.84

The temperature of the pressure cell was then lowered from 20.5° C. to 1° C. over 18.97 hours at a constant cooling rate by circulating cooling/heating fluid through the cell jacket while stirring at 600 rpm. The actual pressure of the cell and the temperature were monitored during the cooling. The time and temperature at which the measured pressure began to deviate from the expected pressure (as calculated based on the temperature and initial pressure) were taken to be the gas hydrate formation onset time and temperature. The rapid hydrate formation time and temperature were taken to be the point at which the temperature of the cell contents began to increase due to the exothermic hydrate formation process. This is illustrated for the hybrid mixture of Synthesis Example 24, as shown in the FIGURE.

The Onset Temperature and Time and the Rapid Hydrate Formation Temperature and Time for the polymers of Synthesis Examples 22-25 are given in Table 2. Also in Table 2 are the Onset Temperature and Time and the Rapid Hydrate Formation Temperature and Time for distilled water in the absence of a gas hydrate inhibitor polymer and the Onset Temperature and Time and the Rapid Hydrate Formation Temperature and Time for a 50 mL solution of Luvicap 55W, which is a commercial fully synthetic gas hydrate inhibitor available from BASF.

TABLE 2 Evaluation of polymers. Rapid Rapid hydrate hydrate forma- forma- Onset Onset tion tion C P_(start) Time Temp time temp Experiment Polymer [ppm] [bar] [min] [° C.] [min] [° C.] Evaluation Synthesis 5000 77.72 315 15.7 373 14.8 Example 1 Example 22 Evaluation Synthesis 5000 77.32 325 15.5 478 12.9 Example 2 Example 23 Evaluation Synthesis 5000 77.84 499 12.5 519 12.2 Example 3 Example 24 Evaluation Synthesis 5000 77.6  486 12.7 550 11.7 Example 4 Example 25 Comparative No — 77.27 184 17.9 303 16 Evaluation polymer Example 1 Comparative Luvicap 5000 77.33 422 13.9 751 8.3 Evaluation 55W Example 2

As can be seen in Table 2, the inventive polymers lowered both the Onset Temperature and Rapid Hydrate Formation Temperature compared to when no polymer was added and increased the Onset Time and Rapid Hydrate Formation Time compared to when no polymer was added. In addition, the inventive polymers compared favorably to the commercial kinetic gas hydrate inhibitor polymer with respect to the Onset Time and Rapid Hydrate Formation Time.

All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention.

While particular embodiments of the present invention have been illustrated and described herein, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the range and scope of equivalents of the claims and without departing from the spirit and scope of the invention. 

1. A method of inhibiting gas hydrates comprising: contacting a gas hydrate with a hybrid mixture formed by combining at least one ethylenically unsaturated monomer with a solution of at least one naturally derived hydroxyl containing chain transfer agent and a non-metal ion initiator at a temperature effective to initiate polymerization of the at least one ethylenically unsaturated monomer and the naturally derived hydroxyl containing chain transfer agent, wherein the naturally derived hydroxyl containing chain transfer agent is a hydroxyl containing moiety obtained from plant sources directly or by enzymatic or fermentation processes.
 2. The method of claim 1 wherein the naturally derived hydroxyl containing chain transfer agent is a polysaccharide.
 3. The method of claim 1 wherein the naturally derived hydroxyl containing chain transfer agent is a polysaccharide.
 4. The method of claim 1 wherein at least one naturally derived hydroxyl containing chain transfer agent is a monosaccharide or a disaccharide.
 5. The method of claim 4 wherein the at least one naturally derived hydroxyl containing chain transfer agent is selected from the group consisting of glucose, galactose, mannose, fructose, arabinose, xylose, maltose, lactose, trehalose, cellobiose, maltotriose, and sucrose and combinations thereof.
 6. The method of claim 1 wherein the at least one ethylenically unsaturated monomer is a vinyl lactam or a vinyl lactam with a co-monomer.
 7. The method of claim 6 wherein the ethylenically unsaturated monomer is N-vinyl pyrrolidone or vinyl caprolactam or combinations thereof.
 8. The method of claim 1 wherein the chain transfer agent has an average molecular weight of about 100,000 or less.
 9. The method of claim 1 wherein about 35% to about 90% by weight of the hybrid mixture is derived from the naturally derived hydroxyl containing chain transfer agent.
 10. The method of claim 1 wherein about 40% to about 60% by weight of the hybrid mixture is derived from the naturally derived hydroxyl containing chain transfer agent.
 11. The method of claim 11 wherein the initiator is an azo initiator, a tert-butyl hydroperoxide and erythorbic acid redox system, and peroxide and an amine.
 12. The method of claim 12 wherein the azo initiator is selected from the group consisting of 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2′-Azobis(2-methylpropionamidine)dihydrochloride, 2,2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2′-Azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride, 2,2′-Azobis[2-(2-imidazolin-2-yl)propane], 2,2′-Azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride, 2,2′-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethl]propionamide} and 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and combinations thereof.
 13. The method of claim 2 wherein the polysaccharide is a hydrolyzed starch having a dextrose equivalent of 9 or greater.
 14. The method of claim 2 wherein the polysaccharide is maltodextrin having a dextrose equivalent of about 13.0 to about 17.0
 15. The method of claim 1 wherein the at least one ethylenically unsaturated monomer is anionic.
 16. The method of claim 1 wherein the at least one ethylenically unsaturated monomer is non-anionic.
 17. The method of claim 14 wherein the at least one ethylenically unsaturated monomer is cationic.
 18. The method of claim 14 wherein the at least one ethylenically unsaturated monomer is nonionic. 